Brazil is known for its warm climate, but in recent years heat waves have become more frequent and intense in many regions, from the Center-West to the Southeast and South. Extreme heat affects health, agriculture, water supply, energy use and daily life in cities. Understanding why it happens and how to protect yourself and vulnerable people is increasingly important.
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What is a heat wave?
A heat wave is a period of several consecutive days with temperatures well above normal for a region and time of year. Because "normal" varies from place to place, a temperature that is routine in one city can be a heat wave in another. Brazil's National Institute of Meteorology (INMET) monitors temperatures across the country and issues alerts when temperatures remain significantly above average for several days in a row.
Heat waves are especially dangerous when high temperatures persist at night, because the body doesn't get a chance to recover.
Why heat waves are becoming more common
Climate change
Global warming increases the frequency and intensity of extreme heat events around the world. The World Meteorological Organization confirmed that 2024 was the warmest year on record globally, continuing a long-term warming trend.
El Niño
El Niño is a natural climate pattern marked by warmer waters in the central and eastern Pacific Ocean. It affects weather around the world and can increase temperatures and change rainfall patterns in parts of Brazil, contributing to droughts in the North and heat in other regions.
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Urban heat islands
Cities with lots of asphalt, concrete and buildings and few trees retain more heat than surrounding rural areas. Air conditioners and vehicles add even more heat. As a result, urban neighborhoods can be several degrees warmer, especially at night.
Deforestation and drought
Forests help regulate temperature and humidity. Deforestation and dry soils can make some regions hotter and drier, and droughts reduce the cooling effect of evaporation.
A national record
In November 2023, during an intense heat wave that affected much of the country, the city of Araçuaí, in Minas Gerais, recorded 44.8°C (about 112.6°F), the highest temperature officially measured in Brazil, according to INMET. That period also brought record electricity demand and health alerts in several states.
Health risks
Extreme heat is one of the most dangerous weather hazards. It can cause:
- Dehydration: loss of water and salts through sweat.
- Heat exhaustion: the body struggles to cool itself.
- Heat stroke: a life-threatening emergency in which body temperature rises to dangerous levels.
- Worsening of chronic diseases: heart, lung and kidney conditions can get worse.
- Sleep problems: hot nights make rest difficult, affecting mood and concentration.
Who is at higher risk
- Older adults, whose bodies regulate temperature less efficiently.
- Babies and young children.
- Pregnant people.
- People with chronic diseases or who take certain medications.
- Outdoor workers, such as construction and delivery workers.
- Athletes and people who exercise outdoors.
- People without adequate housing or access to cooling.
Warning signs
Heat exhaustion
Heavy sweating, pale and clammy skin, weakness, dizziness, nausea, headache and muscle cramps. Move the person to a cooler place, loosen clothing, offer water and cool the body with damp cloths.
Heat stroke
Very high body temperature, confusion, hot skin (which may be dry), fast pulse, fainting or seizures. This is an emergency: call emergency services immediately (in Brazil, SAMU at 192), move the person to a cool place and try to lower their body temperature while waiting for help.
How to stay safe
- Drink water regularly, even if you are not thirsty. Avoid excessive alcohol and very sugary drinks.
- Avoid sun exposure during the hottest hours, usually from 10 a.m. to 4 p.m.
- Wear light, loose, light-colored clothing, a hat and sunscreen.
- Keep homes cool: close curtains during the day, ventilate at night and use fans or air conditioning when possible.
- Take cool showers to lower body temperature.
- Eat light meals with fruits and vegetables.
- Reduce intense physical activity during the hottest part of the day.
- Check on older neighbors and relatives, especially those who live alone.
- Never leave children or pets inside parked cars, even for a few minutes.
Protecting pets
Animals also suffer in extreme heat. Provide fresh water and shade, avoid walks on hot pavement, which can burn paws, and walk dogs early in the morning or late in the evening. Watch for signs of overheating, such as heavy panting, drooling and weakness.
Heat and the economy
Heat waves increase electricity demand for cooling, put pressure on water supply and can damage crops and livestock. They also reduce worker productivity, especially outdoors. Planning for extreme heat is becoming a priority for governments and companies.
What cities can do
- Plant trees and create green areas to provide shade and cooling.
- Use reflective materials on roofs and pavements.
- Open cooling centers in public buildings during extreme heat.
- Issue early warnings through apps, text messages and media.
- Adjust work schedules for outdoor workers.
- Protect vulnerable populations, including people experiencing homelessness.
Staying informed
Follow forecasts and alerts from INMET and local civil defense agencies. In Brazil, civil defense alerts can be received by text message in many areas, depending on registration and location.
Related reading:
Frequently asked questions
What is the highest temperature ever recorded in Brazil?
44.8°C, recorded in Araçuaí, Minas Gerais, in November 2023, according to INMET.
Why are heat waves becoming more frequent?
Climate change, combined with natural patterns such as El Niño and urban heat islands, increases extreme heat.
What should I do if someone has heat stroke?
Call emergency services immediately, move the person to a cool place and help lower their body temperature while waiting for help.
Who is most at risk during heat waves?
Older adults, young children, pregnant people, people with chronic illnesses and outdoor workers.
Are hot nights dangerous?
Yes. When nights stay hot, the body can't recover from daytime heat, increasing health risks.
How can I keep my home cooler?
Close curtains during the day, ventilate at night, use fans or air conditioning and avoid using the oven during the hottest hours.
Conclusion
Heat waves are a growing challenge in Brazil and around the world. Staying informed through official alerts, taking simple precautions, recognizing warning signs and caring for vulnerable people can prevent serious health problems. At the same time, greener, better-prepared cities will be essential to face a warmer future.